The present invention relates to an electron beam deflector used for a cathode ray tube. More specifically, the invention relates to an electron beam deflector, equipped, in addition to a deflection coil, with a deflection yoke having subcoils for correcting convergence or having subcoils for correcting distortion of figure.
Japanese Patent Laid-Open No. 21053/1982 discloses a deflector that can be adapted to a cathode ray tube that has heretofore been used as a projection tube. According to the deflector of this prior art, coils are arranged in the order of deflection yoke and convergence yoke from the side of the phosphor screen, each of the yokes being independent from each other. The deflection yoke generates a main deflection magnetic field for deflecting the beam, and its output terminals are connected to a deflection output circuit.
The convergence yoke generates a correcting magnetic field such that red, green and blue electron beams come into agreement with each other on the screen. As a result, very small distortion of the figure is corrected. The terminal of the convergence yoke is connected to a convergence adjusting circuit. The above-mentioned structure has now been widely used as a deflector for the projection TV's.
With the above-mentioned conventional structure in which the deflection yoke and the convergence yoke are separated from each other, however, the total length of the cathode ray tube inevitably becomes long, imposing limitation in designing TV sets in compact sizes. When the electron gun has a high magnification, furthermore, problem arises in regard to focusing performance.
Another conventional example for solving this problem has been taught in Japanese Patent Laid-Open No. 198642/1984. According to this conventional example, the vertical subcoil is wound maintaining the same distribution as the vertical deflection coil. In this conventional example, however, no attention has been given in regard to winding the horizontal convergence coil (horizontal subcoil) maintaining the same distribution. Therefore, the deflector for the projection TV which includes horizontal and vertical convergence coils is not helpful for sufficiently reducing the total length of the cathode ray tube.
According to the prior art, therefore, the cathode ray tube has an extended total length due to the presence of convergence yoke. Therefore, limitation is imposed on reducing the size of the cathode ray tube, and satisfactory performance is not obtained for focusing the electron beam. According to the prior art, furthermore, disadvantage is also involved in regard to manufacturing cost.